Divergence is focused on few genomic regions early in speciation: incipient speciation of sunflower ecotypes

Early in speciation, when populations are undergoing the transition from local adaptation to incipient species, is when a number of transient, but potentially important, processes appear to be most easily detected. These include signatures of selective sweeps that can point to asymmetry in selection between habitats, divergence hitchhiking and associations of adaptive genes with environments. In a genomic comparison of ecotypes of the prairie sunflower, Helianthus petiolaris, occurring at Great Sand Dunes National Park (Colorado), we found that selective sweeps were mainly restricted to the dune ecotype and that there was variation across the genome in whether proximity to the non-dune population constrained or promoted divergence. The major regions of divergence were few and large between ecotypes, in contrast with an interspecific comparison between H. petiolaris and a sympatric congener, H. annuus. In general, the large regions of divergence observed in the ecotypic comparison swampe...在物种形成的早期阶段，当种群正从本地适应（local adaptation）向初期物种（incipient species）过渡时，诸多短暂出现但可能具有重要意义的过程似乎最易被检测到。这些过程包括可反映生境间选择不对称性的选择性清除（selective sweeps）信号、分化搭车效应（divergence hitchhiking），以及适应性基因与环境的关联。我们对分布于科罗拉多大沙丘国家公园的草原向日葵（Helianthus petiolaris）生态型开展基因组比较分析后发现，选择性清除主要局限于沙丘生态型，且基因组不同区域是否受非沙丘种群的约束或促进分化存在差异。与细叶向日葵（H. petiolaris）与同域近缘种向日葵（H. annuus）的种间比较结果不同，本研究中生态型间的主要分化区域数量稀少且跨度较大。总体而言，本研究生态型比较中观察到的大型分化区域 swampe...